Kitchin-no mado-o shimeru-no-o wasureta. (I forgot to close the window in the kitchen.)
Situation 1: Mr. and Mrs. Okubo are going out. After leaving the house, Mrs. Okubo realizes that she forgot to shut and lock the window.
妻： あ、いけない！キッチンの窓を閉めるのを忘れた。
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